1. override
double transform(double t)

Returns the value of the curve at point t.

The value of t must be between 0.0 and 1.0, inclusive.

Source 

@override
double transform(double t) {
  assert(threshold >= 0.0);
  assert(threshold <= 1.0);
  if (t == 0.0 || t == 1.0)
    return t;
  return t < threshold ? 0.0 : 1.0;
}